Pulse transmitter



Nov. 5, 1946. w. VAN B. ROBERTS PULSE TRANSMITTER Filed Aug. 1, 1942 NNKN m m: k M ai wzzfizis 0 A: .i A: .i i u imm umm R n 0 M T 35m 53 u cc c c m cm 95% mm 0 98 Qskusm L E E. r E E Ev. mo fibo Mm QEQEQEQEQGEQQsE @EEEEQEQQ M952 Q v 7 [Q vs 8E5: 3R3 QEYSBQQ 328E Patented Nov. 5,1946 I PULSE TRANSMITTER. Walter van B. Roberts, Princeton, N. J.,asslgnor to Radio Corporation of America,

of Delaware a corporation Application August 1, 1942, Serial No. 453,17011 Claims. (Cl. 250-'17) the generator of said waves.

A more specific object is to provide a modulating system which includesa source of constant,

frequency waves, a non-reflecting load, a line connected between thesource and the load, and

' reactance tube network means connected across the line and arranged tocontrol the timin of arrival of waves at the load, with means forcompensating for attenuation of the waves by circuits of the reactancetube network means.

An exposition of the principles underlying the 8 present invention willnow be given: It is known to employ reactance tube circuits whichinclude a multi-electrode vacuum tube having a condenser connectedbetween, the anode and the control grid and a resistor connected betweenthe control grid and the cathode of the tube. A variwaves travelingalong the line will sufier attenuation as well as variations of velocityof propagation. To avoid this undesired attenuation,- it is proposed inaccordance with the invention to introduce a. time delay between thearrival of waves at the phase shifting portion of the reactance networkand the arrival of the waves at the anode-cathode terminals of the tube.The action of the complete network of the invention is best describedwith reference to the accompanying drawing, of which:

Fig, 1 shows, by way of example only, one embodiment of the presentinvention; and

Fig. 2 shows, graphically, the timing variation of pulses travelingalong the system shown in Fig.1. p In Fig. 1, there is shown a pulsetransmitter system which includes a blocking oscillator l adaptedtogenerate relatively widely spaced pulses of constant amplitude andfrequency,

which are fed into a concentric transmission line 2 for subsequentutilization by a transmitter 4 able reactance can thus be obtainedacross the anode and cathode which constitute, in effect, terminals forthe circuit. It is known that such a combination behaves with respect toa sinusoidal voltage applied to the aforesaid terminals like acombination of capacity'and resistance whose magnitudes may be varied byvarying the biasing potential of the control grid of the tube. I havefound, however, that this behaviour is not limited to sinusoidal wavesand that such a reactance tube system behaves like a combination ofcapacity and resistance with respectto waves of any shape whatsoeverimpressed upon the network terminals. A similar result is reached forother reactance tube systems employing phase shifting elements of othernatures than the caand antenna 5. In series with the line 2 and formingpart thereof there are provided loops or adjustable length foldedportions 3, 3, and another line 2'. The folded portions 3 are shown inthe form of lecher wire lines with adjustable sliders, by way ofexample. The transmitter 4 is adapted to convert energy pulses receivedfrom line 2 into corresponding pulses of ultra high frepacity-resistancecombination which is discussed above by way of illustration. 1

Inasmuch as the reactance tube network described behaves like acombination of capacity and resistance, it is now proposed in accordancewith the invention to connect a sumcient number of such reactance tubenetworks across a transmission line to effectively control the ve-.

locity of propagation of waves along said line by varying the effectivedistributed shunt capacity across the line. However, since each of thesenetworks introduces a resistance component as well as a capacitycomponent across the line,

quency waves and to radiate these waves from antenna 5. A number ofidentical reactance vacuum tube circuits l2 are connected across theterminals 9 and II of the folded portions 3 and the outer conductor ofthe transmission line. Each of these networks comprises a. phaseshifting circuit which includes capacity 6 and resistor l in series, andby-pass condenser 8. One armature of condenser 6 is connected toterminal 9 while the other armature of this condenser is connected tothe control grid ofthe reactance tube intimately associated therewith.The resistor 7 and by-pass condenser 8 are connected in series betweenthe ground lead of the cathode and the control grid. This phase shiftingnetwork produces a voltage across resistor 1 as a result of voltageat-terminal 9 of foldedflin por tion 3. The anode [0 of the reactancetube is connected, to the other terminal ll of the folded part 3 so thatanode current produced by the aforesaid grid voltage occurs earlier withrespect to the arrival of a traveling pulse the longer the folded part 3of the line. The result of this is that the anode current pulse may beanalyzed into not only a wattless or energy-less compothan that of theblocking oscillator. est line C of Fig. 2 are shown the pulses of ultrainvention will be achieved so long as the effective velocity ofpropagation along the line'is capable of being varied by the applicationof modulating potential to the grid of the reactance tube. It will beappreciated that the phase or-frequency modulated pulses emanating fromtransmission line 2 may be employed for other purposes than to exciteultra high frequency radiation, if desired.

- pulse will be increased in passing through thesystem Preferably, thelength'of the folded portion 3 should be adjusted to permit the pulseto.

pass-without change of energy. Whereshort" pulses are dealt with, eachreactance tube net-- work l2 producesa certain displacement of thetraveling pulse with respect to its normal position, and any number ofnetworks may be'connected across the line at will. However, theinvention is not limited to such pulses and in case waves having shapesmore nearly sinusoidal are employed, it is preferable to connect aconsiderable number of reactance networks (for example ten or twelve,uniformly spaced) per wavelength measured along the line, In this way,the a line behaves to the operating frequency as though its capacitywere uniformly distributed. Three identical networks are shown in Fig. lof the drawing, but it will be realized that the. actual number employedwill depend uponthe length of the line and the amountpf modulationdesired. f

The grid potential for each of. the reactance tubes is obtained fromlead extending to a e ngle source of modulating voltage which might,forjexample, be audio frequency. In this case,

the pulses arriving at thetransmitter 4 will be phase modulated inaccordance with audio voltage. Howevenit is well known that the audio Ivoltage may be suitably-predistorted so that the pulses arrivingattransmitter 4 are frequency modulated with respect to the originalvoltage prior todistortion.

Fig. 2 represents-along illustrated so that while the average frequencyof arrival is the same as the frequency of the blocking oscillator, yettheir momentary phase or frequency of arrival is alternately greater andless In the lowshort waves'radiated from antenna 5, which pulses aresubstantially identical in position and length but occur with variablefrequency determined by the frequency of the pulses shown in the line 13immediately above.

It will be appreciated that by the use of, the present invention, it isnot necessary to modulate the operation of the blocking oscillator inany respect to obtain a modulation ofthe pulses, as

ajresult of which; the construction of such an oscillator isgreatlysimplified. Furthermore, in view of this advantage of theinvention, the blocking oscillator. may be operated under crystalcontrol for improved stability.

It will also be realized. that the phase shifting v the upper line A theseries of constant amplitude constant frequency pended claims isintended to' designate any shape pulse other than a continuoussinusoidal wave.

What is claimed is: 1. In a transmission system, a source ofnonsinusoidal wave pulses, a transmission line connected to said sourcefor feeding said pulses to a load, means for relatively displacing thepositions of said pulses on said line comprising a phase shiftingcircuit shunted across said line, a vacuum tube excited from said phaseshifting circuit, and

a connection from the output of said tube to said line at a'pointdisplaced along said linefrom the point of connection of said phaseshifting circuit, whereby the energy component of anode current fed intosaid lines reduces the energylosses of said waves traveling along saidline while the energylessccmponent acts effectivelyto shift the posi-1tion of said wave along said line. I

2. A pulse transmitter comprising a source of non-sinusoidal wavepulses, a transmitter of ultra short waves, and a transmission lineextending between'said'source and transmitter, a pluralityof physicallyspaced adjustable line sections inserted in series at differentlocations along said line, a reactance tube network across the terminalsof each adjustable line section corresponding to the junction points tosaid line, and a connection from the control electrodes of saidreactance tube networks to a common source of audio frequency modulatingpotential.

3. A pulse transmitter comprising a source of substantially rectangularwave pulses, a transmitter, aline connection between said source andsaid transmitter, a plurality of lecher w e lines inserted in serieswith said line at different locations along said line, a slider for eachlecher wire line for adjusting the eflective length thereof, a reactancetube network connected across the junction points of each lecher wirewith said line,

, by-pass capacity, a connection from the anode of each tube to theother junction point of its associated lecher wire line which is nearestthe transmitter, and a connection from the grid of each tube to a commonsource of modulating voltage,

' whereby the energy component of anode current circuit connectedacross'the' transmission line 2 at point 9, for example, can take otherspecific forms than that illustrated. The object of the fed into saidline by said first source reduces the energy lossesof the wavestraveling along the line.

4. A pulse transmitter comprising a source of pulses, a utilizationcircuit, a line connected between said source and utilization circuit,and. a

reactance tube network connected to spaced points on said line andhaving a source of modulating voltage connected thereto for varying therelative timing of the pulses along said line, said network including aphase shifting circuit and a vacuum tube. f.

5. A pulse transmitter as defined in claim 3, characterized in this thatsaid reactance is a condenser.

6. A pulse transmitter in accordance with claim 2, characterized in thisthat said networks are uniformly distributed along said line.

7. A pulse transmitter comprising a source of non-sinusoidal wavepulses, a transmitter of ultra short waves, a transmission lineextending between said source and transmitter and having a foldedportion, a reactance tube network across the terminals of said foldedportion, said network including a phase shifting circuit and a vacuumtube, and a connection from a grid of said tube to a source of audiomodulating voltage.

8. A pulse transmitter comprising a source of non-sinusoidal wavepulses, a utilization circuit, and a transmission line extending betweensaid source and utilization circuit, a plurality of physically spacedadjustable line sections inserted in series at difierent locations alongeach wavelength of said line, a reactance tube network across theterminals of each adjustable line section corresponding to the junctionpoints to said line, and a connection from the control electrodes ofsaid reactance tube networks to a common source of modulating potential.

9. A pulse transmitter comprising a source of non-sinusoidal wavepulses, a utilization circuit, a transmission line extending betweensaid source and utilization circuit and having a folded portion, a.reactance tube network across the terminals of said folded portion, saidnetwork including a phase shifting circuit and a vacuum tube, and aconnection from a grid of said tube to a source of audio modulatingvoltage.

10. The method of operating a transmission system including atransmission medium, which comprises generating pulses of asubstantially sion line extending between said, source and utilizationcircuit, a, circuit. providing a delay path for waves passing thereoverconnected between two spaced points on said line, a reactance tubenetwork across the terminals of said circuit, said 7 network including aphase shifting circuit and a vacuum tube, and modulating'means coupledto an electrode of said tube.

WALTER VAN B. ROBERTS.

